The area of the picture is , (20-2x)(12-2x)=84 i.e, Option A
Explanation:
Given,
The length of the outer rectangle = 20 cm
The width of the outer rectangle = 12 cm
The area enclosed by the frame = 84 sq cm
Formula
The area of a rectangle = Length × Width sq m
As per the figure,
The length of the picture = 20-2x [ the frame is x cm wide so, we subtract 2x for both side]
The width of the picture = 12-2x
So, the area of the picture is = (20-2x)(12-2x)
Hence,
(20-2x)(12-2x)=84